Kuberntes Complete Notes.
https://github.com/kubernetes/community/blob/master/icons/README.md
https://kubernetes.io/docs/tutorials/hello-minikube/
https://labs.play-with-k8s.com/
https://killercoda.com/playgrounds/scenario/kubernetes
examples\<object-name>
- Download Binaries
curl -L https://github.com/etcd-io/etcd/releases/download/v3.3.11/etcdv3.3.11-linux-amd64.tar.gz -o etcd-v3.3.11-linux-amd64.tar.gz - Extract
tar xzvf etcd-v3.3.11-linux-amd64.tar.gz - Run etcd service
tar xzvf etcd-v3.3.11-linux-amd64.tar.gz - Assign key values.
./etcdctl set key1 value1 - Get the key value.
./etcdctl get key1
- Authenticate User.
- Validate Request.
- Retrieve Data.
- Update ETCD.
- Communicate with Scheduler.
- Communicate with kubelet.
- Watch Status
- Remidiate Situation
Node Monitor Period = 5s
Node Monitor Grace Period = 40s
POD Eviction Timeout = 5m
wget https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kube-scheduler
cat /etc/kubernetes/manifests/kube-scheduler.yaml
- Register Node
- Create PODs
- Monitor Node & PODs
wget https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubelet
ps -aux | grep kubelet
wget https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kube-proxy
Command to check the pod details node wise:
kubectl get pods -o wide
Command to override the existing definitions:
kubectl replace -f replicaset.yamml
As their name suggests, label selectors allow you to identify the objects you have tagged with particular labels. Label selectors can either be equality-based or set-based. Equality-based label selectors work by specifying an exact value that you want to match against. If you provide multiple selectors, all of them must be satisfied to qualify as a match.
metadata:
name: label-demo
labels:
environment: production
app: nginx
kubectl get pods --selector app=nginx
kubectl get pods --l app=nginx
To add a label to an existing resource, you can use the following command:
# this will create a label “group” with a value of “main”
kubectl label pod/metadata-demo group=main
You can also remove the label using this command:
# remove the “group” label from the resource
kubectl label pod/metadata-demo group-
Update the taints on one or more nodes. A taint consists of a key, value, and effect. As an argument here, it is expressed as key=value:effect.
If a pod has tolerations that match the taints on a node, the scheduler will place the pod on that node. If there are no taints on the node, then any pod with or without tolerations can be scheduled on the node.
The effect must be
- NoSchedule
- PreferNoSchedule
- NoExecute
Currently taint can only apply to node.
USAGE
$ kubectl taint NODE NAME KEY_1=VAL_1:TAINT_EFFECT_1
$ kubectl taint nodes nodename dedicated=special-user:NoSchedule
For Untaint
$ kubectl taint nodes nodename dedicated=special-user:NoSchedule-
You specify a toleration for a pod in the PodSpec. Both of the following tolerations "match" the taint created by the kubectl taint line above, and thus a pod with either toleration would be able to schedule onto node1.
tolerations:
- key: "dedicated"
operator: "Equal"
value: "special-user"
effect: "NoSchedule"
The default value for operator is Equal.
A toleration "matches" a taint if the keys are the same and the effects are the same, and:
- the operator is Exists (in which case no value should be specified).
- the operator is Equal and the values are equal.
This node selector helpful to schedule the pods on to specific node.
First we need to add the labels to the required node.
kubectl label nodes nodename size=t2micro
Then we need to add the below code into the definition file.
nodeSelector:
size: t2micro
Generate POD Manifest YAML file (-o yaml). Don't create it(--dry-run)
kubectl run nginx --image=nginx --dry-run=client -o yaml